The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.
Motor vehicle engines produce torsional vibration that is undesirable to transmit through the powertrain and driveline to the motor vehicle. Typically, a damper is used to isolate or reduce the torsional vibration transmitted to the transmission. The damper is placed within a torque converter between a torque converter lock up clutch and the input shaft of the transmission. However, in certain powertrain configurations the damper is insufficient to isolate the torsional vibrations. For example, in powertrains having fuel efficiency systems such as reduced engine cylinder operation with a forward engine connected to a rearward transmission via a propeller shaft, the lock up clutch in the torque converter must be slipped during reduced cylinder operation, as the damper located between the torque converter and the transmission cannot adequately isolate the torsional vibrations in the connecting propeller shaft.
Accordingly, there is room in the art for a powertrain having a multi-stage damper that reduces torsional vibration to allow complete engagement or nearly complete engagement of a torque converter clutch at successively lower engine speeds while the engine operates with a reduced number of active cylinders.